1. Department of Viroscience, Erasmus MC, Rotterdam, Netherlands.
2. Centre for Immunology of Infectious Diseases and Vaccines, National Institute for Public Health and the Environment, Bilthoven, Netherlands.
3. Department of Medical Microbiology, Amsterdam UMC, Amsterdam, Netherlands.
4. Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10021, USA.
5. Department of Occupational Health Services, Erasmus MC, Rotterdam, Netherlands.